Nanoporous
materials
have attracted tremendous interest due to their many potential applications,
including but not limited to low-dielectric constant (low-k) thin films in
microelectronic industry, membranes and selective permeation filters in
biotechnology, and catalysts in chemical engineering. The
emerging field of engineered nanoporosity (controlling pores from several
angstroms to tens of nanometers ) require vast improvements in pore
characterization techniques, as there are few probes capable of
characterizing such porosity, especially in thin films and especially when the
pores are closed and inaccessible to gas absorption techniques.

Positronium
annihilation lifetime spectroscopy (PALS)
has proven to be a very powerful technique capable of probing unoccupied
nanoscale volumes (both open and
closed), such as nanovoids, nanopores, or defects in a wide
dimension range (0.3 nm to 30 nm). Beam-based
PALS has a particularly advantage capable of depth-profiling very thin films
(from several nanometers to microns thick). As a specific
example of the broadly applicable beam-PALS technique, we focus herein on the
extensive investigation of nanoporous low-k
thin filmsto demonstrate PALS
capability in exploring pore characteristics on
nanoscale. Cu/porous low-k
integration issues, such as metal
diffusion, diffusion barrier integrity and the
compatibility of low-k films to integration processes. The methodology
developed is perfectly general for applications to varieties of nanoporous
materials.

For a better understanding
of the PALS, a tutorial
section is provided. Details about the PALS
technique and the methodologies of using beam-PALS to explore nanoporous
thin films are described in related publications.
Sample services and contact information are
included.